Open Science is an umbrella term for a variety of different practices in public and private research,. With the growing interest in Open Science, for example through the UNESCO Recommendation on Open Science in 2021, there is also a need for better understanding the diverse impacts of Open Science practices.Based on literature and case studies collected by PathOS, the report presents Key Impact Pathways of Open Science. The approach used for the report was tested in a preceding proof-of-concept study and adapts common evaluation methods and concepts, particularly identifying impact pathways (from activities to the creation of outputs, outcomes, and impacts). The resulting information is used to generate high-level impact pathways, displayed as intervention logics, of Open Science practices. Six such pathways indicating the impacts of different Open Science activities are identified in the report: A Citizen Science pathway illustrates how citizen science interventions correlate with certain impacts such as ‘trust’ stemming from the outcome of engagement of citizens in citizen science projects. Two Open Access pathway were generated through a “downstream” analysis and highlight the diverse effects of two different types of Open Access publishing. One pathway explores the impacts of research data sharing through Open and FAIR Data, showing different economic effects and benefits. An exploratory pathway, due to limited available evidence, discusses the potential impacts of open code and open software sharing. In addition potential pathways for impacts of Open Science on the environment. The findings illustrate the important mediating factor of policy and governance, which can be affected by a broad range of societal aspects. Likewise, another pathway presents the ways Open Science can affect reproducibility. The report shows that both tracing the effects of different Open Science interventions up to the impact stage (“downstream analysis”) and identifying the activities that may create certain academic, societal, and economic impacts (“upstream analysis”) are feasible. While the approach is overall confirmed, the results also point to the need for further research in terms of topical coverage and types of evidence, as well as limitations to the causal claims for Open science impacts.